A wireless communication system is a complex network of systems and elements. Typically elements include (1) a radio link to the mobile stations (e.g., cellular telephones), which is usually provide by at least one and typically several base stations, (2) communication links between the base stations, (3) a controller, typically one or more base station controllers or centralized base station controllers (BSC/CBSC), to control communication between and to manage the operation and interaction of the base stations, (4) a call controller (e.g., a mobile switching center (MSC)) or switch, typically a call agent (i.e., a “softswitch”), for routing calls within the system, and (5) a link to the land line or public switch telephone network (PSTN), which is usually also provided by the call agent.
Typically, a mobile station communicates with a base station via a reverse link. In particular, the reverse link includes a number of channels such as a reverse pilot channel, a reverse fundamental channel (R-FCH), and a reverse dedicated control channel (R-DCCH). In IS2000 cellular systems, for example, the reverse pilot channel is always used for transmission of power control, synchronization, and may be used for location information associated with the mobile station. In contrast, the reverse fundamental channel and the reverse dedicated control channel may or may not be used depending on the service provided to the mobile station. The reverse fundamental channel is used primarily for transmission of traffic information such as voice or data input from the mobile station during a call whereas the reverse dedicated control channel is used for transmission of control information and data. Even though the reverse fundamental channel may also be used for transmission of control information by embedding that information within the traffic information, the reverse dedicated control channel operates at lower average power than the reverse fundamental channel to transmit such information to a base station. In particular, the reverse dedicated control channel may be operable for discontinuous transmission (i.e., no transmission of audio or data information from the mobile station) to reduce power consumption.
One aspect of designing a wireless communication system is to optimize the resources available to the wireless communication system. For example, a mobile station user typically makes selections to retrieve voice mails or information regarding a bank account by simply pressing keys on the mobile station such that voice input is not necessary. Touch tones such as dual-tone multiple frequency (DTMF) tones are generated in response to the selections made by the user. Accordingly, encoded DTMF messages corresponding to the DTMF tones are transmitted by the mobile station to the base station via the reverse fundamental channel of the reverse link. In this case, unnecessary information such as encoded audio information generated from the user's voice and background noise are also transmitted along with the tones via the reverse link. As a result, interference is increased as more of the reverse link capacity is occupied to transmit the unnecessary information. Further, control information from a mobile station may be transmitted as needed whereas encoded audio information may be transmitted continuously. Thus, more power is consumed by the mobile station to transmit encoded audio information when a voice input is not required to be sent. Control information sent on an as needed basis where as voice information is always sent.
Therefore, a need exists to control the reverse link to limit the transmission of unnecessary information to reduce interference within the communication system and to reduce mobile station power consumption.